Start mechanism for telegraph selector



y 1969 G. c. MEYERS ET AL 3,445,592

START MECHANISM FOR TELEGRAPH SELECTOR Filed Oct. 19, 1965 '0 'IIIIIIII-INVENTORS GORDON c. MEYERS RICHARD L. VESSEL AT TOR Y United StatesPatent U.S. Cl. 178-33 6 Claims ABSTRACT OF THE DISCLOSURE A mechanismfor assuring that the start lever of a telegraph selector will notinterfere with the operation of the selector magnet armature thereofincluding an open portion on the selector magnet armature and acooperating abutment on the start lever for permitting the startlever tomove to a position over the armature without interfering with theoperation of the armature and a pair of levers pivotally mounted on aportion of the orientation mechanism of the selector and operated by theselector start cam for moving the start lever otf of its pivotperpendicularly of the armature to a displaced position during thereceipt of the information bits of a character by the selector magnet,then for moving the start lever away from the armature along a pathextending parallel to the armature, then for moving the start leverperpendicularly of the armature back onto its pivot and then for movingthe armature into engagement with the armature during the receipt of thestop pulse of the character by the selector magnet.

In telegraphy, to which this invention is most applicable, intelligenceis transmitted from one station to another by way of seriatim electricalimpulses carried over a conductor usually called a telegraph line. Eachimpulse is a binary bit, and these binary bits are represented on thetelegraph line by the presence or absence of electrical current flowingthrough the line. The presence of current is called a mark and theabsence of current is called a space. These binary bits are combinedinto groups of bits with each different group forming a discretealphanumeric character, and one cycle of operation of a teletypewriterreceiver is used to receive each character. Each charac er is normallymade up of five character-designating code bits and two synchronizingbits which function to distinguish one character from another as signalsare received over the telegraph line. A spacing synchronizing bit(called a start pulse) precedes the first code bit each character tosignify the start of that character, and 'a marking synchronizing bit(called a stop pulse) follows the last code bit of each character tosignify the end of that character.

From time to time the telegraph line experiences periods of idlenesswhen no characters are being transmitted. The telegraph line thenremains in the marking (presence of current) condition that it assumedduring the stop pulse from the last character transmitted. Whentransmission is resumed and receipt of the first character begins, thetelegraph line assumes its spacing (start pulse) condition. Therefore,whenever the telegraph line is in its marking condition, during the stoppulse of the previous character or an idle period in the line, theteletypewriter receiver mus be prepared to begin receipt of a newcharacter at any time that the telegraph line changes from its markingcondition to its spacing condition. Occurrence of this spacing conditionon the telegraph line indicates the start of receipt of the nextcharacter and causes the teletypewriter receiver to begin a new cycle ofoperation.

The portion of a teletypewriter receiver which receives electricalimpulses over a telegraph line is called the "ice selector. A selectorconverts the seriatim code bits of each character into simultaneouslongitudinal displacements of mechanical levers thereby converting theelectrical representation of the character received over the line into amechanical representation in the displacement of the levers.

In start-stop telegraph receiving selectors, the first bit of eachcharacter is a synchronizing bit which starts the receiving selector inoperation for one machine cycle. The start lever that senses thepresence of this start bit must, in the case of a magnetic receivingselector, sense a movement of an armature from the idle-line condition(marking) to the start bit condition (spacing) without unduly loadingthe armature. Excessive loading of the armature distorts the operationof the selector and results in a loss of accuracy or selector operatingmargin. To avoid this, the start lever can be lightly rested against anabutment on the armature and apply a light loading perpendicular to thepath of armature movement as shown in Patent No. 2,595,745, granted toW. J. Zenner on May 6, 1952. When the armature moves from themarking-stop position to the spacing-start position, the start leverslips off of the armature abutment and moves perpendicularly to the pathof armature travel so as to fall in over the armature. The start levermust then either be removed quickly from the path of movement of thearmature before the first code bit is received by the magnet or thestart lever and armature abutment may be so shaped that the start levermay permit armature movement without first being withdrawn as shown inFIG. 18 of Patent No. 2,192,351, granted to E. E. Kleinschmidt on Mar.5, 1940. Even this latter alternative, however, necessitates that thestart lever be withdrawn at some point in the machine cycle. If thestart lever is not withdrawn at the beginning of the machine cycle as inthe Zenner patent mentioned above, it can be withdrawn at the end of thecycle as in the above-mentioned patent to Kleinschmidt. Sincewithdrawing of the start lever in either of the cited alternativesnecessitates immobilizing the armature for a substantial time, the startlever cannot be withdrawn during the receipt of the code bits after thestart pulse and before the stop pulse.

Since telegraph signals are subject to distortion as they pass from atransmitting station to a receiving station over a transmission channel,the code bits within these telegraph signals are sampled at theirmidpoints. In order to adjust the sampling point of the code bits fordifferent conditions of distortion, each telegraph receiver is equippedwith a range adjustment that varies the timing relationship between theincoming telegraph signals and the mechanism that samples the armatureposition at predetermined instants in each machine cycle. This isaccomplished by moving start and stop controls for the clutch thatdrives the armature sampling mechanism.

It is an object of the present invention to increase the speed oftelegraph apparatus by resetting the adjustable start mechanism of avariable-start-position, start-stop telegraph selector during thecode-receiving portion of the machine cycle.

It is another object of the invention to start a machine cycle of amagnet-operated telegraph selector at a variable start location withoutimmobilizing the magnet armature for a substantial period of time duringthe machine cycle.

According to the preferred embodiment of the invention, a te egraphselector cam sleeve is selectively coupled to a rotating shaft by atwo-cycle-revolution clutch. When the selector armature having an openframework goes from its marking-stop position to its spacing-startposition, an undercut start lever rotates on its pivot into the areavacated by the now spacing armature. This trips the selector clutch forone cycle of operation as shown in Patent No. 3,033,926, granted to T.I. Przysiecki on May 8, 1962; but unlike the start lever of thePrzysiecki patent, the start lever now remains in this position duringthe start of the selector cycle with the armature free to assume eitherone or the other of its two possible conditions due to the undercut inthe start lever and the open framework of the armature. As the selectorcam assembly rotates, it operates a follower that raises the start leveroff of its pivot and completely clear of the armature. Later in thecycle, another cam follower moves the start lever out of the directionof the path of armature travel. The first cam follower then lowers thestart lever back onto its pivot and into the level of the armature.During the stop pulse of the telegraph signal and toward the end of theselector cycle, the other cam follower permits the start lever to restagainst the end of the marking armature awaiting the receipt of a newspacing start pulse.

A more complete understanding of the invention can be had by referringto the following detailed description when considered in conjunctionwith the accompanying drawing wherein:

FIG. 1 is a view of the start mechanism during the stop or idlecondition of the telegraph line;

FIG. 2 is the same view as shown in FIG. 1 with the exception that thecam is rotated to a position corresponding to a later time in the cycleof the selector and during receipt of a character; and

FIG. 3 is a view in perspective of the selector armature and start leverand showing the selector magnet.

Referring now to the drawing wherein like reference numerals designatethe same parts throughout the several views, and more particularly toFIG. 3, the two wires of a telegraph line are connected to two coils ofa selector electromagnet 11. These two coils are interconnected by astub wire 21 so that they are connected in series with the telegraphline 10. The U-shaped core 13 of the selector magnet 11 is arranged sothat its two legs pass through the two coils of the selector magnet 11in series magnetically and so that the open ends of the U-shaped core 13form two magnetic poles 14 that are bridged by an armature 15. Thearmature 15 is firmly mounted on a lightweight, open framework armatureextension 16 which is pivoted at its right end on a pin 17 mounted tothe frame 18 of the teletypewriter receiver. Therefore, the armature isfree to move toward the poles 14 whenever current flows through thetelegraph line 10 thereby energizing the coils of selector magnet 11 andcausing magnetic flux to flow through the magnetic circuit comprisingcore 13 and armature 15. A spring 19, attached to armature eX- tension16, pulls armature 15 away from poles 14 whenever current does not flowthrough the coils of selector magnet 11.

With this arrangement, the leftmost end 20 of armature extension 16assumes the position shown in FIG. 3 whenever the telegraph line is inits marking condition and assumes the position indicated by the dottedlines in FIG. 3 whenever the telegraph line is in its spacing condition.Thus, the position of the armature extension 16 is a mechanicalrepresentation of the electrical condition of the telegraph line.

In order that the selector of the teletypewriter may convert theseriatim electrical code bits into simultaneous mechanicaldisplacements, a rotating, multiple-cam sleeve is started at thebeginning of each character and stopped at the end of each character.This cam sleeve provides the timing by which the selector of ZennerPatent 2,595,745 converts these seriatim armature-extension positionsinto simultaneous mechanical displacements. The selector mechanismdescribed herein is identical with the selector of the Zenner patentexcept for the start mechanism and for the use of a two-cycle selectorwherein one character is received in each half revolution of theselector cam sleeve.

The start of the operation of the selector mechanism is controlled by astart lever which is urged to move 4 to the right and to rest anabutment surface 30 formed on its end against the leftmost end 20 of thearmature extension 16 whenever the selector magnet 11 is idle awaitingthe start of a character. When a spacing start pulse is received by themagnet 11 over the telegraph line 10, armature extension 16 is droppedby the magnet 11 to the spacing position shown by the dotted lines inFIG. 3. The abutment surface 30 on start lever 25 is no longer blockedby the leftmost end 20 of armature extension 16 and, therefore, startlever 25 moves rapidly to the right to the position shown in dottedlines in FIG. 3.

The start lever 25 has an undercut portion 31 adjacent the abutment 30and the armature extension 16 has an open portion between the end 20 andthe armature 15. Therefore, although the right end of the lever 25 isover the extension 16, the lever 25 permits the open-structured armatureextension 16 to immediately assume its marking condition again inresponse to a marking condition of the first code bit of the character.Thus, although the start lever 25 stays in its right-hand position, asindicated by the dotted lines in FIG. 3, the start lever does notinterfere with the movement of the armature extension 16 since itsleftmost end 20 is free to move up or down in the undercut portion 31and since the tip of the lever 25 is not aligned with any solid portionof the extension 16.

As most clearly shown in FIG. 1, the start lever 25 is pivoted at itslower extremity on a fixed post 35 that is mounted to the frame of theteletypewriter. The start lever 25 is urged to rotate clockwise aboutfixed post 35 by a spring 36 and, when the armature extension 16 movesto its spacing position, the spring 36 rotates the start lever 25clockwise about the fixed post 35 thereby moving the surface 30 to theright into the position shown in dotted lines in FIG. 3. Start lever 25has a lug 40 extending from its midsection which ex ends into a slot 41formed in a start ball 42. Start bail 42 is pivotally mounted on aranging pivot 45 so that when the start lever 25 moves to the right thelug 40 in the slot 41 moves the start bail 42 to the right therebyrotating the start bail 42 clockwise about the ranging pivot 45. Firmlyfixed to the start bail 42 is a stop arm 46 that is also pivoted onranging pivot 45 so that when start bail 42 rotates clockwise aboutranging pivot 45, it carries stop arm 46 with it. A bent-over lip 47 onthe end of stop arm 46 is used to control the starting and stopping of aselector clutch 49 of the type shown and described in Nelson Patent2,566,031 granted Aug. 28, 1951.

The driven member of the selector clutch 49 carries a control tab 48(FIG. 1) on its periphery. Whenever control tab 48 is blocked frommovement, the driven member of the clutch abruptly disengages from thedriving member and stops. Whenever control tab 48- is unblocked, theclutch 49 engages and the driven member rotates with the driving member.Whenever stop arm 46 is in its counterclockwise extreme as a result ofsurface 30 on start lever 25 being held to the left of leftmost end 20of armature extension 16, lip 47 is maintained in interfering relationwith tab 48 of the selector clutch and the driven member of the clutch49 is maintained disengaged from the driving member thereof.

As is fully set forth in the above-identified Zenner 2,595,745 patentthe driving member of the selector clutch 49 is connected to acontinuously rotating drive shaft 50 which provides continuous inputdrive power to the selector mechanism. The driven member of the selectorclutch 49 is attached to a selector cam sleeve 51 that is rotatablymounted on drive shaft 50 so that whenever the selector clutch isengaged, selector cam sleeve 51 is coupled through the selector clutchto drive shaft 50 and rotates with drive shaft 50 until the tab 48 onthe selector clutch is again blocked by lip 47 on stop arm 46.Therefore, when the telegraph line changes from the marking condition tothe spacing condition and armature extension 16 drops to the positionshown by the dotted lines in FIG. 1, the start lever 25 moves to theright under the action of spring 36 thereby rotating start bail 42 andstop arm 46 about ranging pivot 45 to remove lip 47 from engagement withtab 48 on the selector clutch. This permits the selector clutch toengage and couple the selector cam sleeve 51 to the drive shaft 50 inorder to convert the seriatim electrical code impulses into simultaneousmechanical displacements.

As soon as start lever 25 moves to the right as shown in dotted linesinFIG. 1, it is lifted olf of its pivot 35 permitting the start lever tobe moved leftwardly without interfering in any way with the operation ofthe armature extension 16. When surface 30 on start lever 25 has beenmoved to the left of leftmost end of armature extension 16, start leveris then lowered onto its pivot 35 and permitted again to rest itssurface against the leftmost end 20 of armature extension 16 during thestop pulse at the end of the character.

To control these timed movements of start lever 25, a start cam 56 isfirmly mounted on selector cam sleeve 51 to rotate with the selector camsleeve. As soon as start lever 25 falls in over armature extension 16during the spacing start pulse of a character, the selector clutchbegins rotating selector cam sleeve 51 and start cam 56 with it. Theselector considered herein is a two-cycle selector in that the selectorstarts and finishes receipt of a character in 180 of rotation of theselector cam sleeve 51. Therefore, the start cam '56 contains twoidentical cam profiles around its periphery.

A lifting lever 57 is pivoted on ranging pivot 45 and is biased torotate counterclockwise about ranging pivot 45 by a spring 58 that isattached to a spur 59 projecting downwardly and to the right fromlifting lever 57. The upper end of lifting lever 57 is formed into acamfollower portion 61. Spring 58 serves to hold cam-follower portion 61in engagement with the start cam 56.

When selector cam sleeve 51 and start cam 56 begin rotating with shaft50 from the position shown in FIG. 1, a ramp 63 on start cam 56 drivescam follower 61 rightwardly rotating lifting lever 57 clockwise aboutpivot 45 against spring 58. When lifting lever 57 rotates clockwise alifting arm 64 on lifting lever 57 rises and engages a spur 66 on thebottom of start lever 25.

As ramp 63 on start cam 56 rocks lifting lever 57 clockwise aboutranging pivot 45, lifting arm '64 continues to rise and lifts startlever 25 off of its fixed pivot (FIG. 2) until abutting surface 30 ishigh enough to clear the leftmost end 20 of armature extension 16 evenwhen the armature extension is in its marking condition. Cam-followerportion 61 on lifting lever 57 then rides on dwell portion 67 of startcam 56, holding start lever 25 off of fixed pivot 35.

In FIG. 2 start cam 56 is shown rotated to a position corresponding to alater time in the cycle of the selector after the lifting arm 64 hasraised start lever 25 suificiently to clear armature extension 16. Atthis time a cam-follower 68 on start bail 42 is engaged by a ramp 69 onstart cam 56 which is identical to ramp 63 but displaced from it aboutstart cam 56 by 180. As start cam 56 continues to rotate, ramp 69 pushesstart bail 42 to the left (FIG. 2) and as start bail 42 moves to theleft, it rotates counterclockwise about ranging pivot 45 thereby drivingthe lip 47 on stop arm 46 into the path of a second control tab 48 onthe selector clutch 49. Since the selector receives a character duringeach half-revolution of rotation, the selector clutch 49 is stoppable ineither of two rotational positions, 180 apart. To stop in either of tworotational positions, the selector clutch has two control tabs 48 eachidentical to the tab shown in FIG. 1. As lip 47 on stop arm 46 is movedinto a position to engage the next clutch control tab 48 the leftwardmovement of start bail 42 also moves start lever 25 to the left by meansof the engagement of lug on start lever 25 with the slot 41 on startbail 42. The cooperation of ramp 69 and cam-follower 68 thus moves startlever 25 leftwardly until surface 30 on start lever 25 is to the left ofleftmost end 20 of armature extension 16. At this time, cam-followerportion 61 on lifting lever 57 drops oif of an edge 71 on start cam 56thereby permitting lifting lever 57 to rotate counterclockwise under theaction of spring 58 about ranging pivot 45, lowering lifting arm 64 andlowering start lever 25 onto fixed pivot 35.

After ramp 69 and cam follower 68 have moved abutment surface 30 to theleft of leftmost end 20 of extension 16, cam follower 68 rides a dwellportion 72 (identical to dwell portion 67 but displaced by on start cam56. When all of the code bits of the character have been received by theselector, the telegraph line assumes its marking stop condition. Duringthis marking stop pulse, an edge 74 on start cam 56 passes cam follower68 permitting spring 36 to move start lever 25 and start bail 42 to theright. Cam follower 68 then begins to fall into a notch 76 on start cam56, but abutment surface 30 on start lever 25 strikes leftmost end 20 ofarmature extension 16 preventing cam follower 68 from falling into notch76. As cam follower 68 tries to fall into notch 76, the next control tab48 on the selector clutch 49 strikes lip 47 on stop arm 46 therebystopping the selector cam sleeve 51 to await the start of the nextcharacter. The start mechanism is then in the condition shown in FIG. 1awaiting the receipt of the spacing start pulse of the next character.

In telegraphy, each code bit is subject to distortion as it travels overthe telegraph line. The extent and type of distortion is dependent uponthe particular telegraph line. Therefore, a modern telegraph selector ismade capable of accurately receiving signals having a wide variety oftypes of distortion. Since all of the code bits are of the same finitechronological duration, it is usually best to sample each code bit, witha selector of the type shown in the Zenner patent, near itschronological center. Since telegraph lines vary, a given selector isusually adjusted in place after installation and periodicallythereafter. The selector adjustment that moves the selector samplingpoint with respect to the center of each code bit is called the rangeadjustment. Since the center of each code bit is always measured fromthe beginning of the start pulse, the range adjustment can best be madein the start mechanism of the selector which actually determines thetime at which the selector clutch engages and rotates the selector camsleeve that in turn controls selector timing.

In FIG. 1 start bail 42, stop lever 46, and lifting lever 57 are allpivoted on ranging pivot 45. Ranging pivot 45 corresponds to stud 38 inthe Przysiecki 3,033,926 patent mentioned above and is similarly mountedon the teletypewriter frame so that it can be moved in a fixed arc aboutthe axis of drive shaft 50. The range adjustment of the selector isaccomplished by moving the ranging pivot through its fixed arc. As theranging pivot is moved through its fixed arc, poor reception willusually be noticed as the ranging pivot reaches either extreme position.The points on the fixed arc where poor reception begins are then notedand ranging pivot 45 is placed midway between these points.

In order to sample the code bits later than their chronological center,the ranging pivot 45 is moved clockwise (FIG. 1) about the center ofdrive shaft 50 moving lip 47 on stop arm 46 clockwise about the centerof drive shaft 50. This causes the selector clutch to stop at a moreclockwise position. Since selector cam sleeve 51 rotatescounterclockwise, it takes the selector cam sleeve longer to arrive atthe same angular position after starting from its new position, thussampling each bit later. In order to sample the code bits earlier, theranging pivot 45 is moved counterclockwise about the center of driveshaft 50, moving lip 47 to a position that is more angularly advanced inthe direction of selector cam-sleeve rotation. Therefore, selector camsleeve 51 still starts at the beginning of the start pulse but from anangularly advanced position and with this head start arrives at eachsampling position earlier.

Lifting lever 57 is also mounted on ranging pivot 45 in order that thetime relationship between the start of selector cam sleeve 51 and theraising of start lever 25 oif of fixed pivot 35 is held constant. Thecurved surface 77 on lifting arm 64 is provided to engage with spur 66on start lever 25 no matter where ranging pivot 45 is placed.

Since armature extension 16 does not move with ranging pivot 45, startlever 25 is mounted on the fixed pivot 35. Slot 41 and lug 40 permitrelative movement between start lever 25 and start bail 42 about thecenter of drive shaft 50.

OPERATION The spacing start pulse permits extension 16 to drop so thatstart lever 25 rocks to the right. Rightward movement of start lever 25rotates start bail 42 clockwise about ranging pivot 45 carrying camfollower 68 into notch 76. Clockwise rotation of start bail 42 rotatesstop arm 46 clockwise about ranging pivot 45, removing lip 47 fromengagement with control tab 48 (FIG. 1) on the selector clutch. Thispermits the selector clutch to begin rotating selector cam sleeve 51.When start cam 56 begins rotating, ramp 63 starts to rotate liftinglever clockwise raising lifting arm 64. Lifting arm 64 raises startlever 25 clear of armature extension 16. Another ramp on start cam 56moves start bail 42 and start lever 25 to the left until lip 47 on stoparm 46 is positioned to block the next control tab of the selectorclutch and until start lever 25 has moved to the left of armatureextension 16. A lip on start cam 56 then lets lifting lever 57 lowerstart lever 25 back down to its original position. The other lip onstart cam 56 then lets abutting surface 30 of start lever 25 restagainst leftmost end 20 of armature extension 16 during the marking stoppulse to await the next spacing start pulse.

What is claimed is:

1. In a start-stop telegraph signal receiver the combination of:

a signal controlled receiving magnet having an armature;

a cam;

a rotary driver for the cam;

a clutch for connecting the cam to the rotary driver;

a start lever for sensing a movement of the armature;

.a pivot for supporting said start lever for oscillation in a pathextending parallel to the armature;

a clutch-trip lever operated by the start lever in response to amovement of the armature for tripping the clutch to establish a drivingconnection through said clutch from the driver to the cam;

means operated upon the sensing by the start lever of a movement of thearmature for lifting the start lever off of the pivot and for moving thestart lever in a path substantially parallel to the path of movement ofthe armature; and

means operated by the cam for moving the start lever in a pathsubstantially perpendicular to the path of movement of the armature.

2. The combination according to claim 1 wherein the cam operated meansfor moving the start lever is a cam follower mounted on the clutch-triplever.

3. A printing telegraph receiving selector including:

a pivot member;

a start lever mounted on the pivot member;

a start cam;

means responsive to movement of the start lever for operating the startcam;

means responsive to operation of the start cam for displacing the startlever with respect to the pivot member to a shifted position, and

means responsive to operation of the start cam for pivoting the startlever in the shifted position.

4. The selector according to claim 3 wherein the pivoting means is alever mounted in engagement with the start lever for actuation therebyand positioned for engagement by the start cam for actuation thereby.

5. In a telegraph selector mechanism of the type including a selectormagnet having an armature, a fixed pivot, a start lever normally mountedon the fixed pivot in engagement with the armature and monuted formovement from a first to a second position in response to movement ofthe armature, a clutch, a clutch trip lever connected to the start leverfor tripping the clutch in response to movement of the start lever tothe second position and an orientation mechanism including an adjusablepivot for supporting the clutch trip lever and for varying the positionof the clutch trip lever with respect to the start lever to compensatefor signal distortion, a device for moving the start lever out of thesecond position and thereby freeing the armature for response toincoming signals including a lever mounted on the adjustable pivot formoving the start lever off the fixed pivot and means responsive tomovement of the start lever from the first to the second position foroperating the lever.

6. The device accrding to claim 5 wherein the selector mechanism furtherincludes a constantly rotating drive shaft and a cam sleeve mounted onthe drive shaft, wherein the clutch operates to couple the sleeve to theshaft for rotation therewith and wherein means for operating the leverincludes a cam mounted on the sleeve in engagement with the lever forrocking the lever about the adjustable pivot to lift the start lever offthe fixed pivot.

References Cited UNITED STATES PATENTS 2,505,729 4/1950 Zenner 17s 252,595,745 5/1952 Zenner 178-33 5,033,927 5/1962 Moebius 17833 THOMAS A.ROBINSON, Primary Examiner.

U.S. Cl. X.R. 17827

